The invention concerns in general a device for measuring the angle and/or angular velocity of a rotatable body, and, in particular, a device for measuring the angle and/or angular velocity of a rotatable body and/or of the torque acting on it.
A very exact determination of a rotational angle is necessary for many systems, e.g., in the automotive industry. A specific application of such a device is a steering-wheel angle sensor, whereby enormous safety requirements exist.
A device is made known in DE-A-195 06 938 belonging to the applicant, which said device is used to measure the angle and/or the angular velocity of the rotatable body, in particular a body that can be rotated by more than 360°, according to the preamble of claim 1. In the case of the known device, the first and second devices are each formed out of a toothed wheel with associated angle sensor, whereby the two toothed wheels—when the numbers of teeth are different—are in mesh with one toothed wheel that is mounted on the steering-wheel shaft. Using a modified vernier method, the angle of the steering axle can therefore be determined from the current angular and/or phase difference between the two toothed wheels. This device therefore offers the advantage that multiple rotations can be detected, but it is disadvantageous in that the detection takes place by means of the interconnection of toothed wheels and therefore not in a contactless manner. Moreover, the installation space required for such a device is relatively large, making it difficult to integrate it, particularly on the steering axle, where the multi-function switches are also accommodated. Finally, a laborious evaluation using an arc tangent method is required to measure the individual rotational angles.
Furthermore, diverse angle sensors are known that are based on contactless detection. They are generally not suited to measuring angles with great accuracy. These devices and methods also require expensive evaluation circuits and algorithms or, alternatively, they have insufficient accuracy or an insufficient measuring range if the device is suited only for use with small angles, for example.
There is a need, therefore, for an improved device for measuring the angle and/or the angular velocity of a rotatable body and of the torque acting on it. It is an object of the present invention to further develop a generic device—as was made known in DE-A-195 06 939, for example—having at least first and second devices that output different signals to an evaluation circuit in response to a rotation of the body in such a fashion that it takes up very little space and makes a simple evaluation and determination of the angle possible, whereby the detection is to take place in contactless fashion overall.